One thing you might want to keep in mind...

I have a Priority Club pass and am pretty happy with it. I fly many different airlines but lately have been using United a lot, flying into and through Chicago (ORD).
Its great that an airport you fly through has agreements with several lounges but the distance from your gate to that lounge has to be taken into account.
At ORD, the United lounge is not part of Priority Pass and the hike (and I mean HIKE... 20+ minute walk) to another lounge can make it unfeasible. This happens a lot at the major airports. To get to a lounge usually requires you having to go to some far away terminal.
Some lounges are even terminal side (rather than airside), meaning you would have to go through security again to get back to your gate.